IXP: Internet Exchange Point

Internet Exchange Points - acronym of (IXP) or (IX) - form an integral
part of the physical structure of the Internet. Internet Exchange
Points allow Internet computer networks - specifically Internet
Service Providers (ISPs) - to exchange traffic (data routing) across
their networks.

Internet Exchange Points have evolved from: Federal Internet Exchanges
(FIX), Network Access Points (NAP) and Commercial Internet Exchanges
(CIX). Each of these exchanges were created to transition the Internet
away for government agencies (in the early 1990s), and allow commercial
networks to access and eventually become the backbone of the Internet.

Transferring data long distance (transatlantic for example) could/can
be prohibitively expensive for ISPs without access to an IXP; who
only have/had access to a single upstream transit provider. IXPs
allow ISPs to link their networks and "cut" upstream transit
providers out of the equation.

Internet Exchange Points are useful to ISPs for a number of reasons:

Cheaper to traffic data through IXP's than an upstream transit
provider.

Improved network performance.

Increased bandwidth.

Low latency.

More control.

Out of all the reasons why an ISP will traffic data through an
IXP: cost is usually the primary reason. Many IXP's are non-profit
organisations (like LINX: London Internet
Exchange): so traffic routed through the IXP (LINX) will be free
for ISPs; the only cost an ISP will have is the membership fee to
join the IXP. IXP's tend to restrict membership to only ISPs; and
refuse contact with members of the public - directing member of
the public to chat to their ISP if an error occur with traffic routed
through the IXP. LINX, for example, has members from: Europe, North
America, Asia and Africa; who are able to exchange traffic "freely"
across continents.

The primary technology (2014) that IXPs use is a network switch; previously
it was a network hub. Each ISP connects to a port on the IXP network switch.
A network switch is more efficient than a hub, because a message is only sent
to the port (ISP) which requests it; not to every port, like with a hub. The
technology which IXPs use is continually evolving: LINX, for example, were
the first IXP to implement a 100-megabit switch and is the 3rd largest (worldwide)
IXP.